This invention relates to a solid state current source circuit and, more particularly, to a precision current source having ripple rejection characteristics whereby the magnitude of current provided therefrom remains substantially constant with variations in the magnitude of the power supply voltage applied thereto. The current source may be utilized to provide a regulated DC output voltage across a load that is coupled to ground reference potential.
The prior art is replete with various types of current sources and voltage regulator circuits for supplying constant output currents and DC regulated voltages. Most of these types of circuits work quite well in environments wherein little or no variation in the magnitude of the supply voltage is permitted. However, many such systems are adversely affected by excessive noise transient spikes that may create large variations in the supply voltage line.
For example, in magnetic bubble memory sensing systems the power supply present is required to provide currents of one ampere peak to the x and y field coils of the bubble memory. These currents are switched at the field rotation frequency, between 50 and 200 KHz, with rise and fall times within 200 nanoseconds. This switching can cause voltage transient spikes to appear on the supply line that can otherwise prevent detection of the magnetic bubble since the magnitude of these spikes are large with respect to the magnitude of a bubble present signal.
Thus, there is a need for a current source circuit that can be utilized to provide a DC regulated voltage which exhibits excellent ripple rejection characteristics. Such a circuit could be employed in a bubble memory sense system, for instance, to reject high frequency components of the switching transients.